Mutation tests refactoring
Merge branch 'master' of https://github.com/DynamoDS/Dynamo

Conflicts:
	src/DynamoCore/TestInfrastructure/MutatorDriver.cs
Attribute class added
Merge branch 'master' of https://github.com/DynamoDS/Dynamo
Merge branch 'master' of https://github.com/DynamoDS/Dynamo
@Benglin Here are some updates code according to your notes.

Brief changes description:
MutationTestAttribute was added to all mutation tests in order to distinguish Mutation tests classes from others in DynamoCore (it simplifies process of launching these mutation tests).
MutatorDriver class contains only basic methods for test launching, it also obtains all mutation tests from current assembly and runs them on the current workspace.
Merge pull request #2208 from vdemedetskaya/master

Mutation test refactoring